Java Junit

Standard Tests

• Keep tests focused on a single behavior.
• Avoid testing multiple conditions in one test method.
• Make tests independent and idempotent (can run in any order).
• Avoid test interdependencies.

Data-Driven (Parameterized) Tests

• Use @ParameterizedTest to mark a method as a parameterized test.
• Use @ValueSource for simple literal values (strings, ints, etc.).
• Use @MethodSource to refer to a factory method that provides test arguments as a Stream, Collection, etc.
• Use @CsvSource for inline comma-separated values.
• Use @CsvFileSource to use a CSV file from the classpath.
• Use @EnumSource to use enum constants.

Assertions

• Use org.junit.jupiter.api.Assertions or AssertJ for more fluent assertions.
• Use assertThrows / assertDoesNotThrow for exception testing.
• Group related assertions with assertAll.

Mocking and Isolation

• Use a mocking framework like Mockito to create mock objects for dependencies.
• Use @Mock and @InjectMocks annotations from Mockito to simplify mock creation and injection.
• Use interfaces to facilitate mocking.

Test Organization

• Group tests by feature or component using packages.
• Use @Tag to categorize tests (e.g., @Tag("fast"), @Tag("integration")).
• Use @TestMethodOrder(MethodOrderer.OrderAnnotation.class) and @Order to control test execution order when strictly necessary.
• Use @Disabled to temporarily skip a test method or class, providing a reason.
• Use @Nested to group tests in a nested inner class for better organization and structure.